1. Field
The present embodiments relate to a non-volatile semiconductor memory device.
2. Description of the Related Art
As an electrically rewritable and highly integratable non-volatile semiconductor memory device, a NAND flash memory is known. The memory cells of the NAND flash memory each include a semiconductor substrate, a charge accumulation layer formed on the substrate via a tunnel insulating film, and a control gate stacked on the charge accumulation layer via an inter-gate dielectric film. Each memory cell stores data in a non-volatile manner using the charge accumulation state of the charge accumulation layer.
In the NAND flash memory, the memory cells are degraded as the number of write/erase operations increases, thus making it hard to store data correctly. As a result, a malfunction may occur in reading data.